In an internal combustion engine mounted on an automobile, for example, a throttle valve of this engine is mechanically connected to an accelerator pedal so that the valve is driven in accordance with the depth of pedaling of the accelerator pedal, that is, the pedaling stroke thereof. With the engine of this type, therefore, an operator can control the engine output, that is, the torque to be transmitted to a driving shaft of the automobile, by adjusting the opening of the throttle valve by means of the accelerator pedal.
In recently offered engines for automobiles, the accelerator pedal and the throttle valve are electrically connected without being mechanically connected to each other, in contrast with the conventional case, whereby the opening of the throttle valve is adjusted and then the engine output is controlled. According to this attempt, when the accelerator pedal is first worked, its pedaling stroke is detected by means of a sensor, and the target output of the engine, that is, the target torque of the driving shaft of the automobile, is determined in accordance with a signal from the sensor. Meanwhile, an electric motor is connected to the valve shaft of the throttle valve, and this electric motor drives the throttle valve so that the opening of the throttle valve corresponds to the aforesaid target torque.
When electrically controlling the engine output, as described above, the target torque of the driving shaft is unconditionally determined in accordance with the pedaling stroke of the accelerator pedal. Therefore, the actual torque of the driving shaft should preferably be changed following up the target torque without delay. After the pedaling stroke of the accelerator pedal is actually changed, that is, after the target torque of the driving shaft is changed, however, a delay, until the actual torque of the driving shaft reaches to the target torque depending on this change, is inevitably caused. As for this delay, it includes a delay corresponding to a time interval which elapses from the instant that air passes through the throttle valve until a suction stroke in which the air is sucked into a cylinder chamber of the engine through a surge tank and compression and explosion strokes for a fuel-air mixture in the cylinder chamber are undergone. If the automobile is furnished with an automatic transmission, moreover, there is a delay in transmission of power attributable to the torque ratio of a torque converter in a power transmission path which extends from the output shaft of the engine to the driving shaft.
After the opening of the throttle valve is changed, as mentioned before, if a delay is caused until this change appears as a change of the actual torque of the driving shaft after undergoing the processes of production and transmission of the aforesaid power, the drive of the automobile cannot be satisfactorily controlled in accordance with the pedaling stroke of the accelerator pedal, that is, the opening of the throttle valve.
This invention has been contrived in consideration of these circumstances, and its object is to provide an output control apparatus for an internal combustion engine, capable of shortening the response time which elapses from the instant that a target torque of a driving shaft of an automobile is determined until an actual torque of the driving shaft attains to the target torque, thereby ensuring a satisfactory drive of the automobile.